This is the best part of this article for me. A lot of solo bootstrappers don't get it. They struggle. But the fact is that you have to market and sell. Talk to customers and do the shittiest but most important thing: Support. No matter how much automation you create, clients will send you emails and say "I cannot do anything. please help" before even explaining what exactly is broken.
There is a lot of dirty work you have to do every day as a bootstrapper and you get no relief from it. You can surely add team members or "outsource" some of it, but you can never outsource talking to clients (both pre sales and post).